Process for synthesizing specific complete mixed polyol esters

ABSTRACT

Reacting a partial polyol monocarboxylic acid ester with an acidic anhydride in the presence of 2,4,6-trinitrobenzene sulfonic acid catalyst to produce specific complete mixed polyol esters, especially synthetic cocoa butter, with substantially no ester group rearrangement.

I Unlted States Patent [1 1 [111 3,882,155

Wharton May 6, 1975 PROCESS FOR SYNTHESIZING SPECIFlC OTHER PUBLICATIONSCOMPLETE MIXED POLYOL ESTERS [75] Inventor: Harry WhitneyWhartomColerain ggg gi zgg at chemical Abstracts Township, HamiltonCounty, Ohio I lribe, et al., Chemical Abstracts, Vol. 77, 1305892 {73]Assignee: The Procter & Gamble Company, (1972) Cincinnati, Ohio Filed:1973 Primary ExaminerDonald G. Daus [2!] Appl No; 415,034 AssistantExaminerD. G. Rivers [52] US. Cl. 260/4103; 260/4048; 260/4106; ABSTRACT260/469; 260/476 R; 260/ Reacting a partial polyol monocarboxylic acidester IIEL C07! with an acidic anhydride in the presence f 2 4 6 [58]held of Search 260/491 trinitrobenzene sulfonic acid catalyst to producespe- 260/4106 cific complete mixed polyol esters, especially syntheticcocoa butter, with substantially no ester group rear- [56] ReferencesCited rangement.

16 Claims, No Drawings PROCESS FOR SYNTHESIZING SPECIFIC COMPLETE MIXEDPOLYOL ESTERS BACKGROUND OF THE INVENTION This invention relates to aprocess for synthesizing complete mixed polyol esters, that is, polyolesters having at least two different ester groups and no hydroxylgroups. More particularly, this invention relates to a process foresterifying partial polyol esters without rearrangement of ester groupseither by intermolecular or intramolecular acyl group exchange. The termpartial polyol ester is used herein to denote a polyol which ispartially, that is, incompletely, esterified and as a consequencecontains at least one hydroxyl group.

In general, this process provides mixed polyol esters with specificester groups at specific polyol hydroxyl sites. Thus, this process isespecially useful for providing synthetic cocoa butter and closelyrelated oleaginous substitutes from inexpensive raw materials such aslard and palm oil.

Cocoa butter is unusual among naturally occurring fats in that it isnormally a brittle solid up to 77F, has a relatively narrow meltingrange and is almost completely liquid at 95F, or slightly below bodytemperature. These unique melting characteristics make cocoa buttersuitable for use in confectionery products, especially chocolates. Suchmelting characteristics contribute glossy coatings, absence ofstickiness and favorable volume changes during confectionery productmolding.

Because of these advantageous melting characteristics and because of thedemand for the properties which cocoa butter imparts to confectioneryproducts, large quantities of this expensive commodity are imported evenwhen domestic fats which can be used to produce synthetic cocoa butterare in plentiful supply at much less than the cost of cocoa butter. Formany years, therefore, attempts have been made to provide from readilyavailable and cheaper fats a product that can be used to replace atleast part of the cocoa butter in chocolates and other confectioneryproducts that normally contain cocoa butter.

In this search for a synthetic cocoa butter, it has been determined thatits advantageous physical characteristics are derived from thearrangement of the fatty acid substituents in its glycerides. Analyticaltests have shown that cocoa butter comprises principallylpalmitoyl-2oleoyl-3-stearoyl glycerol, and minor amounts oftriglycerides having a different order of substitution of the palmitoyl,oleoyl and stearoyl groups on the glycerol molecule. Accordingly,l-palmitoyl-Z- oleyl-3-stearoyl glycerol would provide the desired cocoabutter substitute, were this compound readily available.

With most esterification procedures, the synthesis of such substantiallypure specific triglycerides is impossible since substantial ester grouprearrangement occurs during esterification of specific partialglycerides, namely, monoand diglycerides, the synthesis of which isknown in the prior art. Thus, acylation of l,3- diglycerides with oleicacid and a conventional acid esterification catalyst provides only aminor proportion of triglycerides having an oleoyl group at the 2-position, where this group must necessarily occur to provide the desiredsynthetic cocoa butter.

Feuge, Willich and Guice, the Journal of the American Oil ChemistsSociety, July, l963, pp. 260-264, demonstrate that ester grouprearrangement ordinarily occurs during the esterification of partialglycerides, and, at page 260, point out that hydrochloric, sulfuric andhydrocarbyl sulfonic acids, which are widely used as esterificationcatalysts, cause ester group rearrangement. Accordingly, these acidcatalysts are not suitable for preparing the desired position-specific(i.e., 2 oleoyl) triglycerides for use as a cocoa butter substitute.Similarly, ester group rearrangement ordinarily occurs duringesterification of partial polyol esters other than glycerides, e.g.,during esterification of partial l,2-propylene glycol esters.

One known method for synthesizing a cocoa butter substitute comprisesreacting a diglyceride having pal mitoyl and stearoyl groups at the land3-positions with oleoyl chloride; see U.S. Pat. No. 3,012,890.Furthermore, it is known in the prior art that, in general, acidchlorides can be used to specifically esterify monoand diglycerides. Theuse of acid chlorides for specific esterification-is has manyundesirable aspects, however. For instance, acid chlorides are verycorrosive and their use involves handling problems. Besides,hydrochloric acid, a by-product of the reaction of an acid chloride witha hydroxyl group, is difficult to remove from the oleaginous reactionproduct, a critical factor inasmuch as the product is to be used as afood.

U.S. Pat. Nos. 3,410,88l and 3,337,596 disclose the use of perchloricacid as an effective catalyst for preparing a cocoa butter substitutewithout rearrangement of the ester groups. However, mixtures of organiccompounds with perchloric acid are known to be explosive and its use inthe presence of organic compounds is preferably avoided.

It has now been found that 2,4,6-trinitrobenzene sulfonic acid catalyzesthe esterification of partial polyol esters without ester grouprearrangement. U.S. Pat. No. 3,] l9,849 discloses the esterification ofmonoand diglycerides without interesterification and with an aromaticsulfonic acid, e.g., p-toluene sulfonic acid. The patent does notdescribe the employment of 2,4,6- trinitrobenzene sulfonic acid in thepreparation of triglycerides without ester rearrangement. Moreover, thepreviously noted Feuge, et al. article suggests that sul fonic acidesterification catalysts per se cause group rearrangement.

It is therefore an object of this invention to provide an improvedprocess for synthesizing specific complete mixed polyol esters,especially specific mixed triglycerides. It is a further object toprovide a process for synthesizing specific complete mixed polyol esterswith substantially no rearrangement of ester groups either byintermolecular or intramolecular exchange. It is a further object hereinto provide a process for synthesizing specific complete mixed polyolesters without using perchloric acid or acid chlorides. Yet anotherobject of this invention is to provide a process for the preparation ofsynthetic cocoa butterv These and other objects are obtained herein aswill be seen from the following disclosure.

SUMMARY OF THE INVENTION According to this invention, it has been foundthat specific complete mixed polyol esters, i.e., those with specificester groups at specific polyol hydroxyl sites, can be prepared byesterifyin g partial polyol esters with acid anhydrides in the presenceof a catalytic amount of 2,4,6-trinitrobenzene sulfonic acid attemperatures from about 30F to about 350F.

DETAILED DESCRIPTION OF THE lNVENTlON The 2,4,6-trinitrobenzene sulfonicacid used herein as the catalyst in the position-specific esterificationprocess is a known compound. The compound and a method for preparing itis described in Beilsteins Handbuch der Organischen Chemi'e, 4 ed., Vol.11, p. 80. A suitable method for its preparation involves reaction ofpicryl chloride in an alcoholic solvent with excess sodium bisulfite.

The partial polyol esters to be esterified in the manner of thisinvention are derived from polyols selected from the group consisting ofl) aliphatic diols where the hydroxyl groups are unsymmetricallysubstituted with respect to the carbon chain, or (2) aliphatic polyolscontaining at least three hydroxyl groups These diols and polyols arepreferably those esterified with acyl substituents derived frommonocarboxylic acids containing from 8 to 22 carbon atoms, although theposition-specific esterification is independent of this chain length.

Partial polyol esters derived from aliphatic diols include for example,esters derived from l,2-propylene glycol, l,2-butanediol and1,3-butanediol. Partial polyol esters derived from aliphatic polyolscontaining at least three hydroxyl groups include, for example, es tersderived from glycerin, 1,2,4-butanetriol, erythritol, arabitol, xylitol,1,2,6-hexanetriol, sorbitol and mannitol. The ester groups of thesepartial polol esters include, for example, those derived from caprylic,capric, lauric, myristic, palmitic, stearic, oleic, linoleic, linolenic,arachidic and behenic acids.

Partial polyol esters which are preferred for use herein are partialglyceride esters including 1- and 2 monoglycerides and 1,2- and1,3-diglycerides. The monoglyceride ester groups can be saturated orunsaturated. The diglycerides include disaturated, monoaciddiglycerides, e.g., distearin; disaturated, diacid diglycerides, e.g.,l-palmitoyl-3-stearoyl glycerol, diunsaturated, monoacid diglycerides,e.g., diolein; diunsaturated, diacid diglycerides, e.g., l-oleoyl-3-palmitoleoyl glycerol; and monounsaturated, monosaturated, diaciddiglycerides, e.g., l-palmitoyl-3 palmitoleoyl glycerol. The termsdiacid" and monoacid" are used herein to denote glycerides having twodifferent acyl substituents and one kind of acyl substituentrespectively. The preparation of partial polyol esters for use in theinstant process is fully described in Mattson and Volpenhein, Journal ofLipid Research, July, 1962, vol. 3, No. 3., pages 281-296.

Specific partial carboxylic acid esters of 1,2- propylene glycol canalso be used in the present process. Most l-mono-fatty acid esters ofl,2-propylene glycol. such as l-propylene glycol mono-stearate, can beprepared by reacting l,2-propylene glycol with a desired fatty acid,such as stearic acid, in the presence of a catalyst, such as p-toluenesulfonic acid, and in a solvent, such as xylene, and the l-fatty acidester separated by fractional crystallization, for instance. 2-Mono-fatty acid esters of l,2-propylene glycol, such as 2-propyleneglycol monobehenate, can be prepared by acylation of an appropriatelyblocked l,2-propylene glycol derivative, such as l-tetrahydropyranylpropy lene glycol, with an acid chloride, such as behenoyl chloride, andcleavage of the blocking group in the presence of boric acid.

The symmetrical acidic lipid anhydrides which are preferred for use inesterifying the above partial polyol esters have the structural formula:

wherein each X is a substituent selected from the group consisting of:

1. alkyl and alkenyl groups containing from 7 to 2l carbon atoms andhaving the formula 2. residues of alkyl and alkylene half-esters of adicarboxylic acid having the formula 3. residues of monoacyl diolhalf-esters of a dicarboxylic acid having the formula RCOHCR CHOCR 4.residues of diacyl glyceride half-esters of a dicarboxylic acid havingthe formula II II N RCOCH RCOCHCH OCR and 5. residues of monoacylderivatives of a primary monohydroxy monocarboxylic acid having theformula n 3 RCOR wherein R is selected from the group consisting ofalkyl and alkenyl substituents having from 7 to 21 carbon atoms and Y isselected from the group consisting of benzoyl, p-nitrobenzoyl and alkylphosphoryl substituents of the formula wherein R is a C, to C alkyl orphenyl substituent. These unsymmetrical acid anhydrides are fullydescribed in U.S. Pat. No. 3,337,596, incorporated herein by reference.

The acid lipid anhydrides in the present process can be prepared inwell-known fashion by admixing the corresponding acidic lipid with anexcess of acetic or propionic anhydride, cooling the reaction product,crystallizing the acid lipid anhydride and collecting the desiredproduct by filtration. The unsymmetrical anhydrides are prepared asdescribed in U.S. Pat. No. 3,337,596.

The most effective processes for the formation of acidic lipidanhydrides useful in this invention employ metathesis with acetic anhydride either at low temperatures, i.e., 32 to 140F., with perchloricacid catalysis, or at higher temperature, i.e., 140 to 300F., withoutperchloric acid catalysis, but with evaporation of the acetic acidformed in the reaction.

Acidic lipids for use in preparing the acidic lipid anhydrides by theabove methods can be derived from a variety of sources, depending on thespecific acidic lipid involved. The acidic lipids for use herein includealiphatic monocarboxylic acids, alkyl half-esters of dicarboxylic acids,monoacyl diol half-esters of dicarboxylic acids, diacyl glyceridehalf-esters of dicarboxylic acids, and monoacyl derivatives of primarymonohydroxy monocarboxylic acids.

The monocarboxylic acids contain from 8 to 22 carbon atoms and include,for example, stearic and oleic acids. They can be readily obtained fromglycerides by saponification, acidulation and isolation procedures or byhydrolysis. The acid desired determines the choice of glyceridicmaterial. For example, a technical grade of stearic acid can be obtainedfrom hydrogenated soybean oil and a technical grade of oleic acid can beobtained from olive oil.

The alkyl half-esters of dicarboxylic acids are condensation products ofdicarboxylic acids having from 4 to 6 carbon atoms with straight chainfatty alcohols containing 8 to 22 carbon atoms. Useful dicarboxylicacids include succinic, glutaric and adipic acids. Useful alcoholsinclude, for example, cetyl and octadecyl alcohols. The dicarboxylicacids are advantageously condensed with the fatty alcohols in a mutualsolvent such as dimethylformamide, dimethylacetamide, dioxane, xylene ortoluene, either with or without the use of a catalyst such as sulfuricacid, p-toluene sulfonic acid, hydrogen chloride, zinc chloride, andother such catalysts. These preparations are best carried out withreaction temperatures in the range of from 175 to about 350F. with waterbeing removed under reduced pressure. The desired condensation productsare isolated by appropriate distillation, and/or washing, and/orcrystallization treatments if such treatments are required to removesolvents, excess reactants and impurities.

The monoacyl diol half-esters of dicarboxylic acids are the reactionproducts of monoacyl diols and dicarboxylic acid anhydrides. The diolsfor use in preparing these lipids contain from 2 to 6 carbon atoms andcan contain either primary or secondary hydroxy groups. Useful diolsinclude, for example, ethylene glycol, 1,2- propylene glycol,1,3-propanediol, 1,4-butanediol, 1,3 butanediol and 1,5-pentanediol. Anexcess of one of these diols is condensed with a straight chainmonocarboxylic acid, containing 8 to 22 carbon atoms, such as stearic oroleic acid, in the presence of an esterification catalyst, such assulfuric acid, and preferably with refluxing with xylene. Thiscondensation reaction yields a monoacyl diol which in turn is reacted ata temperature ranging from 175 to 350F. with the anhydride of adicarboxylic acid containing 4 to 6 carbon atoms such as succinic,glutaric and adipic acids, to form the desired lipid.

The diacyl glyceride half-esters of a dicarboxylic acid are reactionproducts of diacyl glycerides and dicarboxylic acid anhydrides. Thediacyl glycerides for use in preparing these lipids contain acyl groupsderived from straight chain monocarboxylic acids containing from 8 to 22carbon atoms, such as stearic and oleic acids, and can be prepared asdescribed in the previously referred to Mattson and Volpenheinreference. These diacyl glycerides are reacted at a temperature rangingfrom 175 to 350F. with the anhydride of a dicarboxylic acid containingfrom 4 to 6 carbon atoms, such as succinic, glutaric and adipid acids,to form the desired lipids.

The monoacyl derivatives of a primary monohydroxymonocarboxylic acid arereaction products of monocarboxylic acid chlorides containing from 8 to22 carbon atoms, such as stearic and oleic acid chlorides, with primarymonohydroxy-monocarboxylic acids having from 3 to 6 carbon atoms.Suitable monohydroxymonocarboxylic acids include hydracrylic, 4-hydroxybutyric, 3hydroxypentanoic, and 6- hydroxyhexanoic acids. Thedesired lipids can be prepared from these acid chlorides andmonohydroxymonocarboxylic acids as described in U.S. Pat. No. 2,251,694.

The unsymmetrical anhydrides useful herein are prepared by reacting thetriethylammonium salt of one acid with the acid halide of the other acidin the manner fully described in US. Pat. No. 3,337,596.

As previously explained, the above partial polyol esters are reactedwith the above acidic lipid anhydrides at a 1:1 mole ratio in thepresence of 2,4,6- trinitrobenzene sulfonic acid catalyst. In apreferred mode, an excess of the acidic lipid anhydride is employed overthat required by the stoichiometry of the reaction; a 10 to molar excessis preferred. The maximum amount of excess lipid anhydride is not critical and molar excesses of 10 to 20 times can be employed, particularlywhen the anhydride is being used as the reaction solvent, as notedbelow. The molar ratio of 2,4,6-trinitrobenzene sulfonic acid to acidlipid anhydride should be at least about 0.001 to l. A maxi mum limit of0.50 to 1 for this molar ratio is most pre ferred, for economic reasons,but higher ratios are operable.

The position-specific esterification reaction of this invention takesplace over a wide range of temperatures and in the presence of a widevariety of solvents without ester group rearrangement. Reaction temperatures can range from 30 to 350F., with 01 to 212F. being preferred. Thereaction can in most cases be carried out at room temperature (ca. 70F).It is noted that the reaction normally occurs at room temperature in atime period ranging from 1 minute to 5 hours. Thus, the reaction of thisinvention is very rapid triacetin using the method of Baur and Lange,Journal of the American Chemical Society, 1951, vol. 73, page 3926.

The following example illustrates the preparation of when compared withesterification with acid chlorides, 5 synthetic cocoa butter in greaterdetail but is not to be which at room temperature normally takes from 10construed in any way as limiting the scope of the invenhours to 24 hoursfor substantial reaction completetion. Unless otherwise specified, allpercentages in the ness. following examples are by weight.

In general, the solvent, if any, can be any organic liquid medium whichwill form a phase sufficiently unil0 EXAMPLEI form so as to bring thereactants into contact. Prefera- Synthetic Cocoa Butter Preparation blyif it is a liquid, a molar excess of the acid lipid anhy- Three hundredand four grams of palm oil hydmge dride is used as the solvent, thisexcess being calculated nated to an iodine value of 8 and having an acidvalue on the basis of only one acidic lipid radical of each anof 0 arereacted with 157 grams of watepwashed and hydride molecule reacting Oheruseful Solvents distilled triacetin in the presence of 26 ml. of sodiumclude chlorinated hydrocarbons such as chloroform methoxide catalyst inthe form of a xykmg Suspension and carbon tetrachloride, aromatichydrocarbons such (009 Sodium methoxide per mL Xylene) at 0 as benzeneand aliphatic esters such as ethyl acetate. with Stirring for hours. Atthis point 58 grams of Still other useful solvents include aromaticheterocyclic glycerd are added; heating and Stirring are contim basesSuch as Pyridine, tertiary amides Such as dimeth 2O ued for one morehour. The reaction mixture is then al- Ylformamide anddimelhylacetamidei heterocyclic lowed to cool with stirring and isstored at room temides such as tetrahydrofuran, and fatty acids. perawrefor 2 days In the case where monoglycerides are the partial Undesirablecomponents are then removed from the polyol esters, the specific solventused seems to have reaction mixture by the following purification pmcesome effect Whether Substantially 8' dure: the solid mass resultingafter the 2-day storage is arrangement occurs; benzene and Pyridine aredesir' slurried with 30 ml. of aqueous acetic acid solution y used asSolvents in this (1353- containing 50% water by volume. The slurry isdis- Turning one Specific application of the solved in 4 litersofethanol-hexane solution (50% ethaabovedescribed general process, thatis, a process for 1 by volume) and the resulting solution cooled topreparing synthetic cocoa butter, it has been found that 50"] Thitemperature i i i d f a 4.1 certain 1,3-diglycerides can be esterifiedwith oleic riod, during which time crystals are formed. At the end acidanhydride by the above-described general method of the 4-hour period,the crystals are separated by vacto provide synthetic cocoa butter. Thisprocess is illusuum filtration and recrystallized overnight from 3liters trated by the following equation: of ethanol-hexane solutionethanol by volume).

O CHOI-l R SO H l 3 Cl7H33CO CHZOC (O)Cl7H35 Oleic anhydride1-palmitoyl-3-stearoyl glycerol (II-1 0C (O) C H CHOC (0) c n1palmitoyl2o1eoyl 3-stearoyl glycerol C 7H CO H The crystals recoveredby filtration are dissolved in 1 liter of ethyl ether and water-washed 3times. The ether is removed by evaporation and the residue crystallizedfrom 2.5 liters of ethanol-hexane solution (50% ethanol by volume) at50F. After filtration the crystals are air dried to provide thesubstantially pure product.

Analysis of the above product shows it to be substantially all1,3-diglyceride containing palmitoyl and stearoyl groups. The aboveproduct has a hydroxyl value of -92 as compared to a theoretical valueof 94.2 for lOO% diglyceride and contains less than 0.5% monoglycerides.it has a complete melting point of 159 to 160F. Analysis for specificacid groups shows the presence of ca. 35% palmitic and ca. 65% stearic,and minor amounts of myristic, all by weight with each acid groupexpressed as the corresponding acid.

Oleic anhydride is prepared by refluxing lOO grams of oleic acid in 300grams of acetic anhydride for three hours. The bulk of the distillablematerial present, mostly acetic acid, is then removed at atmosphericpressure. The residue is then heated at 355F. under 1 to 2 mm. Hg.pressure for 30 minutes to distill the re maining volatile impurities.

Thirteen and one-half grams (13.5 g.) of the 1,3 diglyceride mixtureprepared in the foregoing manner and comprising about 45%l-palmitoyl3-stearoyl glycerol, 42% l,3-distearoyl glycerol, about I l%1,3- dipalmitoyl glycerol, the balance being mixed l,3- diglycerols,were admixed with 26.5 grams of a ll] mixture of oleic acid and oleicanhydride prepared as de scribed above. 0.26 gram of2,4,6-trinitrobenzene sulfonic acid was added to the mixture, theresulting mixture was stirred and maintained at 135F for minutes andthen stirred and allowed to cool to approximately room temperature overa period of 45 minutes. An equal volume of water was added to thereaction mixture, which was then heated to l80F for 1 hour to hydrolyzeexcess oleic anhydride. The water was removed by filtration anddiscarded and the residue extracted five times with equal volumes ofmethanol to remove traces of free acid. The residue was shown by thinlayer chromatography to be substantially pure, i.e. about 94% by weight,triglyceride product.

Analysis for 2position fatty acids by thin layer chromatographyutilizing argentation chromatography showed that the synthetictriglyceride product of Example l contained about 87% by weight of oleicacid esterified at the 2position as compared to 87% to 88% by weight ofoleic acid at the 2position in a commercially available sample of cocoabutter. The percentages of oleic acid are by weight of all acids at the2- position, the acyl group attached thereto being expressed as thecorresponding acid. Accordingly, it is seen that substantially no estergroup rearrangement occurs in this process.

The above procedure is carried out in a solvent amount of dry chloroformwith equivalent results.

The above procedure is carried out at 0 and 2l2F (pressure vessel),respectively, and equivalent results are obtained.

In the above procedure, the oleic anhydride is replaced by an equivalentamount of oleic-benzoic anhydride, oleic-p-nitrobenzoic anhydride andoleicethylphosphoryl anhydride, respectively, and the synthetic cocoabutter 2-oleoyl triglycerides are secured in each instance.

The above procedure is carried out using mole ratios of2,4,6-trinitrobenzene sulfonic acid-to-acidic lipid anhydride of 0.01:]with equivalent results.

EXAMPLE ll Esterification of 1,3-dipalmitin with Oleic Anhydride Twentygrams of l,3'dipalmitin made as described in Example 2 of U.S. Pat. No.2,626,952 and 30 ml. of oleic anhydride made as in Example I herein areadmixed in 50 ml. of water-washed, distilled and dried chloroform in thepresence of 3.3 grams of 2,4,6-

trinitrobenzene sulfonic acid. The reactants are stirred at roomtemperature for 3 hours.

The reaction mixture is dissolved in 500 ml. ethyl ether together with100 ml. water. The ether phase is water-washed 3 times, dried andevaporated in an inert atmosphere. The residue is crystallized twicefrom acetone at 20F and the crystals dried to provide substan tiallypure triglyceride product.

The product has an acid value of ca. 0.8 and a hydroxyl value of 2,0,showing that substantially all the product is triglyceride. Thetriglyceride is found to contain 90-95% by weight oleic acid at the2position, i.e., l-palmitoyl-2-oleoyl-3-palmitoyl glycerol,demonstrating that substantially no existing ester group rearrangementoccurs during the above esterification reaction.

In the above procedure the l,3dipalmitin is replaced by an equivalentamount of l,3-distearoyl glycerol, l-palmitoyl-3-stearoyl glycerol,l-palmitoyl-3-lauroyl glycerol and l-behenoyl-3-stearoyl glycerol,respectively, and the corresponding 2-oleoyltriglycerides are formedwithout ester group migration.

In the above procedure the chloroform is replaced by an equivalentamount of carbon tetrachloride, benzene and hexane, respectively, andequivalent results are secured.

The above procedure is repeated using an equivalent amount ofl,2-dipalmitin as the partial glyceride and l-oleoyldipalmitin issecured, demonstrating that essentially no ester group rearrangementoccurs with the 2,4,6-trinitrobenzene sulfonic acid catalyst herein.

EXAMPLE [I] Esterification of 1,3-dipalmitin with Rapeseed Oil FattyAcid Anhydride Rapeseed oil fatty acid anhydride is formed as follows:rapeseed oil is hydrolyzed to the corresponding rapeseed oil fattyacids. These fatty acids are formed into the corresponding long chainfatty acid anhydrides by the anhydride-forming process disclosed inExample I. The anhydrides so formed are for the most part mixedanhydrides, that is, each anhydride molecule contains two differentfatty acid groups. These anhydrides react in the same manner as if eachmolecule contains two identical fatty acid groups.

Two grams of rapeseed oil fatty acid anhydride, 1.5 grams of1,3-dipalmitin prepared as in Example ll, [0 ml. purified chloroform and0.82 gram 2,4,6- trinitrobenzene sulfonic acid are reacted together withmixing at room temperature (ca. F) for 1 hour. The reaction product isdiluted with 100 ml. ethyl ether, water-washed and the solventevaporated in an inert at mosphere. The residue is crystallized 3 timesfrom ml. acetone at 20F to provide the purified product.

Thin layer chromatography shows that substantially all the product istriglyceride. Analysis of the triglyceride and comparison of the2position fatty acid composition of the triglyceride with the originalrapeseed oil fatty acids indicates that the palmitic, stearic, oleic,palmitoleic, linoleic, linolenic and erucic acid fractions of therapeseed oil each esterify the l,3-dipalmitin at the 2position withsubstantially no acyl group migratron.

EXAMPLE lV Esterification of 2-Monoestearin One-half gram of2-monostearin made by the process described in Martin, Journal of theAmerican Chemical Society, 1953, vol. 75, page 5482, 1.84 grams oleieanhydride made as in Example 1, ml. benzene and 0.033 gram2,4,6-trinitrobenzene sulfonic acid are reacted together with mixing at70F for 3 hours.

The reaction mixture is diluted with ethyl ether, waterwashed and thesolvent removed by evaporation. The residue is crystallized twice fromml. acetone at 20F. Substantially all the product is 2-stearoyldiolein;therefore, substantially no existing ester group rearrangement occursduring the esterification reactions.

In the above procedure, the benzene solvent is replaced with anequivalent amount of pyridine with equivalent results.

EXAMPLE V Esterification of l-Monostearin with Stearoyl Propylene GlycolSuccinate Anhydride Forty-four grams (0.1 mole) of stearoyl propyleneglycol hydrogen succinate are mixed with grams (0.3 mole) of aceticanhydride and heated at reflux for one hour. The mixture is then heatedat 250 to 265F. for 2 hours under a pressure of 25 mm. Hg. The residueis cooled with recovery of about a 96% yield of stearoyl propyleneglycol succinate anhydride (an anhydride having the previously describedstructural formula wherein X is a residue of a rnonoacyl diol halfesterof a dicarboxylic acid).

Three and six-tenths grams of l-monostearin (0.01 mole) prepared by theprocess described in Mattson and Volpenhein, Journal of Lipid Research,July 1962, vol. 3, No. 3, pp. 283, 284, is dissolved in 144 ml. benzenewith slight warming. Nineteen grams (0.022 mole) of the above preparedstearoyl propylene glycol succinate anhydride is added with stirring.The sample is treated with 033 gram 2,4,6-trinitrobenzene sulfonic acidcatalyst and stirring continued at 90F. for 1 hour.

The reaction mixture is diluted with 100 ml. water and the mixtureshaken in a separatory funnel. The washed benzene solution is dried andthe product isolated by chromatography on a 300 gram silica gel 5%water) column. Elution with 1 liter of benzene and with one liter ofbenzene containing 2% ethyl ether and 1% acetic acid yields about I lgrams of product. Practional crystallization of the product from 15volumes of acetone at 70, 50 and 0F. provides a product com prising 90%l-stearoyl-2,3-di(stearoyl propylene glycol succinyl) glycerol havingthe structural formula Substantially no existing ester grouprearrangement occurs during the above esterification reaction.

EXAMPLE VI Esterification of 1,3-Distearin with Octadecyl GlutarateAnhydride Octadecyl glutarate anhydride (an anhydride having thepreviously described structural formula wherein X is a residue of analkyl half-ester of a dicarboxylic acid) is prepared the same as theanhydride in Example V but with substitution of a molar equivalent ofoctadecyl hydrogen glutarate for the stearoyl propylene glycol hydrogensuceinate.

Six and two-tenths grams distearin prepared as in Example of US. Pat.No. 2,626,952 are dissolved in 120 ml. benzene with stirring and slightwarming. Seven and ninetenths grams of the above octadecyl glutarateanhydride are added; when the reagents are completely dissolved, 0.33gram of 2,4,6-trinitrobenzene sulfonic acid is added. The mixture isthen stirred at room temperature for 1 hour.

The reaction mixture is diluted with 100 ml. water and the aqueous layerseparated and discarded. The benzene layer is washed twice with water.dried with five grams sodium sulfate, filtered and evaporated todryness. The residue is crystallized from 200 ml. acetone. The crystalsare recrystallized from 150 ml. acetone to provide 95% purel,3-distearoyl-2-octadecyl glutaryl glycerol. Substantially no existingester group rearrangement occurs during the above esterificationreaction.

EXAMPLE Vll Esterification of 1,3-Distearin withl,3-Distearin-2-Succinate Anhydride 1,3-distearin-2-succinate anhydride(an anhydride having the previously described structural formula whereinX is a residue of a diacyl glyceride half-ester of a dicarboxylic acid)is prepared the same as the anhydride in Example V but with substitutionof a molar equivalent of 1,3-distearin-2-hydrogen succinate for thestearoyl propylene glycol hydrogen suceinate.

Six and two-tenths grams 1,3-distearin are dissolved in 250 ml. benzenewith stirring and slight warming. Fifteen grams of the abovel,3-distearin-2-succinate anhydride are added and dissolved withstirring. When the reagents are completely dissolved. 0.66 gram of2,4,6-trinitrobenzene sulfonic acid is added and the reaction mixturestirred at l00F. for 1 hour.

In order to purify the product, l00 ml. water are added and the aqueousphase separated and discarded. The product is further purified bytreatment with three 30-gram portions of base-form ion exchange resin.The benzene solution is evaporated and the residue crystallized from 200ml. acetone to provide pure di(l,3- distearin) suceinate. Substantiallyno existing ester group rearrangement occurs during the aboveesterification reaction.

EXAMPLE Vlll Esterification of Propylene Glycol Monooleate withStearoyl-4-Hydroxybutyric Anhydride One mole 1,2-propylene glycol isreacted with 0.5 mole oleic acid in one liter of xylene in the presenceof 0.0] mole of p-toluene sulfonic acid catalyst. The sample is refluxedunder a moisture trap for two hours, poured into ice water, water-washedand solventevaporated to provide pure propylene glycol monooleate. Theimpure product is purified with a sil ica gel column to provide about0.35 mole of substantially pure propylene glycol monooleate. Thepropylene glycol monooleate is present as a mixture of isomeric esterswith of the oleoyl groups at the pri mary hydroxyl position and 20% atthe secondary position of LIZ-propylene glycol.

Stearoyl-4-hydroxybutyric anhydride (an anhydride having the previouslydescribed structural formula wherein X is a residue of a monoacylderivative ofa primary monohydroxy monocarboxylic acid) is prepared thesame as the anhydride in Example V but with substitution of a molarequivalent of stearoyl-4- hydroxybutyric acid for the stearoyl propyleneglycol hydrogen succinate.

Three and four-tenths grams of the above propylene glycol monooleate aredissolved in 100 ml. benzene. Ten grams of the abovestearoyl-4-hydroxybutyric anhydride are added to the solution andstirred with slight warming until dissolution is complete. When thereagents are completely dissolved, 0.33 gram 2,4,6- trinitrobenzenesulfonic acid is added and stirring continued at 70F for 1 hour.

In order to purify the desired product, the reaction mixture is dilutedwith 100 ml. water and the aqueous phase is separated and discarded. Thebenzene layer is evaporated to dryness and the residue is dissolved in100 ml. hexane. The hexane solution is crystallized at 50F. to yieldprimarily stearoyl-4-hydroxybutyric acid. The filtrate from the 50F.crystallization is evaporated to dryness and this residue is dissolvedin 200 ml. acetone. The acetone solution on crystallization at 40F.provides oleoyl (stearoyl-4-hydroxybutyryl) propylene glycol. Theproduct consists of a mixture of isomeric esters with 80% by weight ofthe oleoyl groups at the primary hydroxyl position and 20% at thesecondary hydroxyl position of l ,2-propylene glycol. This mixture ofisomers results from the fact that the propylene glycol monooleate usedconsists of an 80-20 mixture of primary and secondary estersrespectively. Thus, substantially no existing ester group rearrangementoccurs during the above esterification reaction.

EXAMPLE [X Esterification of l-Propylene Glycol Monobehenate with OleicAnhydride l-propylene glycol monobehenate is made as follows: ethyllactate(450 grams, 3.8 moles) is mixed with 1.2 ml. concentratedhydrochloric acid and the mixture cooled in an ice bath.Dihydropyran(420 grams, 4.9 moles) is added with stirring, after whichthe sample is allowed to warm to room temperature. After 3 hours, gramsof potassium carbonate are added and the sample stirred. The product isdistilled under reduced pressure with collection of 366 gramstetrahydropyranyl ethyl lactate boiling at 65 to 70C. at 1-2 mm.pressure. Tetrahydropyranyl ethyl lactate(82 grams, 0.46 mole) isdissolved in 300 ml. tetrahydrofuran and the solution is cooled in anacetone-ethanol dry ice bath. The THP ethyl lactate solution is addedslowly to a 10% lithium aluminum hydride solution and subsequently themixture is warmed to room temperature. The reactants are diluted with150 ml. ethanol, followed by 2 liters of water. The sample is thenextracted three times with 400 ml. portions of benzene. The benzeneextracts are dried with sodium sulfate, filtered, and the filtrate isdistilled with collection of the fraction boiling at 78-81C. at 3 mm.pressure. The yield is 28 grams of Z-tetrahydropyranyl propylene glycol.

Z-Tetrahydropyranyl propylene glycol( 16.0 grams, 0.1 mole) isinteresterified with 39 grams methyl behenate using 4 ml. of 40%trimethyl benzyl ammonium methoxide as a catalyst. The reactants arestirred in a 250 ml. flask heated at 6080 C. under a reduced pressure of200 mm. Hg for 6 hours. The reactants are poured into 600 ml. of hexaneand the hexane solution washed with 400 ml. of 1% potassium bicarbonatesolution. The washed hexane layer is diluted with 200 ml. ethanol andgrams urea are added to the sample. Adduct formation with urea isaccomplished by stirring the sample initially at 40C. and allowing themixture to cool at 25C. during a 2-hour interval. The urea adduct isremoved by filtration and discarded. The adduction with urea is repeatedusing 60 grams urea. The filtrate from the second urea adduction iswater-washed three times and the hexane layer is evaporated to dryness.The residue is dissolved in 300 ml. hexane and the solution iscrystallized at 18C. Filtration at 18C. yields 21.3 grams ofl-behenoyl-2-tetrahydropyranyl propylene glycol.1-Behenoyl-2-tetrahydropyranyl propylene glycol (8 grams, 0.0165 mole)is cleaved by reaction with l 1 ml. of 1.6 molar boric acid in trimethylborate. The reactants are heated in a boiling water bath withapplication of vacuum. Heating is continued for 15 minutes with a vacuumof 2-5 mm. Hg pressure during the final 10 minutes. The residue iscooled to room temperature and dissolved in 200 ml. ethyl ether andwater-washed 3 times. The ether phase is dried with sodium sulfate, andevaporated to dryness on an evaporator without warming above 30C. Theresidue is dis solved in 100 ml. petroleum ether and crystallized at70F. The crystals recovered at 70F. are recrystallized from 200 ml.petroleum ether at 50F. to yield ca. 5 grams of l-propylene glycolmonobehenate.

Five grams of the above prepared l-propylene glycol monobehenate aredissolved in 100 ml. benzene together with 6 grams oleic anhydride madeas in Example l. The sample is stirred at room temperature untilsolution is complete. The catalyst, 2,4,6- trinitrobenzene sulfonic acidis added (0.33 gram) and the sample stirred for 30 minutes at roomtemperature.

ln order to purify the product 100 ml. water are added and the aqueousphase separated and discarded. The benzene solution is evaporated todryness and the residue dissolved in 100 ml. acetone. The acetonesolution is crystallized at 0F. with recovery of 95% purel-behenoyl-Z-oleoyl propylene glycol. Substantially no existing estergroup rearrangement occurs during the above esterification reaction.

EXAMPLE X Esterification of 1,4-Distearoyl Erythritol with OleicAnhydride One mole erythritol is reacted with 2 moles methyl stearate in1 liter of dimethylacetamide in the presence of 0.1 mole sodiummethoxide catalyst. The reaction mixture is heated at lO0-120C. underreduced pressure (-100 mm. Hg) for 3 hours with slow distillation ofsolvent such that about 400 ml. of solvent is removed in the 3-hourperiod. Twenty c.c. of 50% by volume aqueous acetic acid are added tothe sample and this mixture poured into 2 liters of water. One liter ofan ethyl acetatebutanol mixture (four parts by volume ethyl acetate toone part by volume butanol) is added. The ethyl acetatebutanol layer isseparated, waterwashed twice and treated with 500 grams urea. Thismixture is stirred at room temperature for 2 hours. The mixture is thenfiltered and 0.12 mole of 1,4-distearoyl erythritol is recovered fromthe urea adduct by dissolving in acetone and crystallizing at 90" v Sixand onehalf grams of the above 1,4-distearoyl erythritol are dissolvedin 200 ml. ethyl acetate with slight warming while stirring. Six andsix-tenths grams oleic anhydride are prepared as in Example I are addedfollowed by 0.33 gram 2,4,6-trinitrobenzene sulfonic acid. The reactionmixture is stirred at room temperature for 1 hour.

In order to purify the product, the reaction mixture is washed 3 timeswith water and the ethyl acetate solution dried with 15 grams of sodiumsulfate and filtered. The solution after crystallizing 24 hours yieldssubstantially pure l,4-distearoyl-2,3dioleoyl erythritol. Substantiallyno existing ester group rearrangement occurs during the aboveesterification reaction.

EXAMPLE XI Esterification of 1,3-dipropanoyl Glyceryl with AceticAnhydride One mole of 1,3-dipropanolyl glycerol is admixed with twomoles of acetic anhydride and dissolved therein with heating andstirring at a temperature of about 175F. 0.5 mole of2,4,6-trinitrobenzene sulfonic acid is admixed with the reactionsolution and the temperature is restored to room temperature (70F) overa 2 hour period. The reaction mixture is poured into 1 liter of waterwhich serves to hydrolyze the unreacted acetic anhydride.

Excess water is removed by -dipropanoyl evaporation at about 90Fv on arotary evaporator, which process also removes much of the acetic acid.The resulting res idue left after evaporation is dissolved in a 1:1mixture of ethyl alcohol and benzene and a 1.0M solution of bariumchloride is added thereto, portionwise, until precipitation of theinsoluble barium acetate monohydrate is complete. The solids are removedby filtration and the benzene-alcohol solvent is evaporated on therotary evaporator under vacuum. The resulting triglyceride product issubstantially pure l-propanoyl-2- acetyl-3-propanoyl glycerol,indicating that the esterification occurs without substantialintramolcular or intermolecular acyl group rearrangement.

The above procedure is carried at and 212F, respectively, withsubstantially equivalent results.

The procedure is carried at a catalyst-toanhydride mole ratio of 0.01:lwith equivalent results.

In the above procedure the acetic anhydride is replaced by an equivalentamount of benzoic acid anhydride and the reaction product issubstantially all 1- propanoyl2-benzoyl-3-propanoyl glycerol, indicatingthat substantially no ester group rearrangement occurs in the process.

What is claimed is:

l. A process for preparing specific complete mixed polyol esters frompartial polyol esters with substantially no ester group rearrangementcomprising esterifying a partial polyol ester with an acid anhydride inthe presence of a catalytic amount of 2 4,6-trinitrobenzene sult'onicacid, said partial polyol ester being selected from the group consistingof partial polyol esters from saturated aliphatic diols having thehydroxyl groups unsymmetrically substituted with respect to the carbonchain and partial polyol esters from saturated aliphatic polyolscontaining at least three hydroxyl groups.

2. A process according to claim 1 wherein said anhydride is selectedfrom the group consisting of acidic lipid anhydrides of the structuralformula 0 an R c x c o wherein X is a substituent selected from thegroup consisting of:

1. alkyl and alkenyl groups having from 7 to 21 carbon atoms and havingthe formula R 2. residues of alkyl half esters of a dicarboxylic havingthe formula 3. residues of monoacyl diol half-esters of a dicarboxylicacid having the formula 9 Z 9 l R-COHCR CHOCR 4. residues of diacylglyceride half-esters of a dicarboxylic acid having the formula 9 o o ln-coca acocaca o'ca and 5. residues of monoacyl derivatives of a primarymonohydroxy monocarboxylic acid having the formula n 3 RCOR wherein in(1) to (5) above:

R is an alkyl or alkenyl group having 7 to 2] carbon atoms; R is analkylene group having 2 to 4 carbon atoms; R is an alkylene group having0 to 4 carbon atoms; R is an alkylene group having 2 to 5 carbon atoms;Z is a substituent selected from the group of hydrogen and methyl; and Yis a substituent selected from the group consisting of benzyl,p-nitrobenzyl, and phosphoryl ester; and wherein the ratio of said2,4,6-trinitrobenzene sulfonic acid catalyst to acidic lipid anhydrideis at least about 0.001 to l. 3. The process of claim 1 which is carriedout at a temperature from 0 to 212F.

4. The process of claim 1 which is carried out using a molar excess ofthe acidic lipid anhydride.

5. The process of claim 1 wherein the partial polyol ester is a partialglyceride ester.

6. The process of claim 1 wherein the partial polyol ester is al.3-diglyceride.

7. The process of claim 1 wherein the partial polyol ester is a partialester of 1,2-propylene glycol.

8. The process of claim 1 wherein the acid anhydride is symmetrical.

9. The process of claim 1 wherein the acid anhydride is an alkylanhydride wherein the alkyl group has from 7 to about 21 carbon atoms.

10. The process of claim 1 wherein the acid anhydride is oleicanhydride.

11. The process of claim 1 wherein the partial polyol ester is amonoglyceride and the reaction is carried out in an organic solventselected from the group consisting of benzene and pyridine.

12. A process for preparing a synthetic cocoa butter comprisingacylating the 2-hydroxyl group of l-palmitoyl-3-stearoyl glycerol witholeic anhydride in the presence of 2,4,6-trinitrobenzene sulfonic acidcatalyst, and crystallizing and separating the synthetic cocoa butterthus formed.

13. A process for preparing synthetic cocoa butter comprising: (1)admixing substantially completely hydrogenated palm oil with glycerol inthe presence of triacetin and sodium methoxide catalyst; (2) separatingand crystallizing the l,3-diglycerides formed; (3) acyl' ating the2-hydroxyl groups thereof with oleic anhydride in the presence of2,4,6-trinitrobenzene sulfonic acid; and (4) crystallizing andseparating the synthetic cocoa butter thus formed.

14. The process of claim 13 wherein the catalyst to oleic anhydridemolar ratio is at least 0.00lt1.

15. The process of claim 13 which is carried out at from about 0 toabout 212F.

16. The process of claim 13 which is carried out in the presence of amolar excess of oleic anhydride.

1. A PROCESS FOR PREPARING SPECIFIC COMPLETE MIXED POLYOL ESTERS FROMPARTIAL POLYOL ESTERS WITH SUBSANTIALLY NO ESTER GROUP REARRANGEMENTCOMPRISING ESTERIFYING A PARTIAL POLYOL ESTER WITH AN ACID ANHYDRIDE INTHE PRESENCE OF A CATALYTIC AMOUNT OF 2,4,6-TRINITROBENZENE SULFONICACID, SAID PARTIAL POLYOL ESTER BEING SELECTED FROM THE GROUP CONSISTINGOF PARTIAL POLYOL ESTERS FROM SATURATED ALIPHATIC DIOLS HAVING THEHYDROXYL GROUPS UNSYMMETRICALLY SUBSTITUTED WITH RESPECT TO THE CARBONCHAIN AND PARTIAL POLYOL ESTERS FROM SATURATED ALIPHATIC POLYOLSCONTAINING AT LEAST THREE HYDROXYL GROUP.
 2. A process according toclaim 1 wherein said anhydride is selected from the group consisting ofacidic lipid anhydrides of the structural formula
 2. residues of alkylhalf-esters of a dicarboxylic having the formula
 3. residues of monoacyldiol half-esters of a dicarboxylic acid having the formula
 3. Theprocess of claim 1 which is carried out at a temperature from 0* to212*F.
 4. The process of claim 1 which is carried out using a molarexcess of the acidic lipid anhydride.
 4. residues of diacyl glyceridehalf-esters of a dicarboxylic acid having the formula
 5. residues ofmonoacyl derivatives of a primary monohydroxy monocarboxylic acid havingthe formula
 5. The process of claim 1 wherein the partial polyol esteris a partial glyceride ester.
 6. The process of claim 1 wherein thepartial polyol ester is a 1,3-diglyceride.
 7. The process of claim 1wherein the partial polyol ester is a partial ester of 1,2-propyleneglycol.
 8. The process of claim 1 wherein the acid anhydride issymmetrical.
 9. The process of claim 1 wherein the acid anhydride is analkyl anhydride wherein the alkyl group has from 7 to about 21 carbonatoms.
 10. The process of claim 1 wherein the acid anhydride is oleicanhydride.
 11. The process of claim 1 wherein the partial polyol esteris a monoglyceride and the reaction is carried out in an organic solventselected from the group consisting of benzene and pyridine.
 12. Aprocess for preparing a synthetic cocoa butter comprising acylating the2-hydroxyl group of 1-palmitoyl-3-stearoyl glycerol with oleic anhydridein the presence of 2,4,6-trinitrobenzene sulfonic acid catalyst, andcrystallizing and separating the synthetic cocoa butter thus formed. 13.A process for preparing synthetic cocoa butter comprising: (1) admixingsubstantially completely hydrogenated palm oil with glycerol in thepresence of triacetin and sodium methoxide catalyst; (2) separating andcrystallizing the 1,3-diglycerides formed; (3) acylating the 2-hydroxylgroups thereof with oleic anhydride in the presence of2,4,6-trinitrobenzene sulfonic acid; and (4) crystallizing andseparating the synthetic cocoa butter thus formed.
 14. The process ofclaim 13 wherein the catalyst to oleic anhydride molar ratio is at least0.001:1.
 15. The process of claim 13 which is carried out at from about0* to about 212*F.
 16. The process of claim 13 which is carried out inthe presence of a molar excess of oleic anhydride.